This invention relates generally to self-powered locomotions, and more particularly concerns a novel uni-wheel skate usable for that purpose.
A survey of devices designed for self-powered locomotion discloses factors which can be improved. The device described herein has many advantages over several time honored and common vehicles.
The improved uni-wheel skate device, as will be seen, is manipulated for self-propulsion in much the same manner as with roller skates or ice skates. All the motions and balance principles are common to walking. The rider alternately rides and strokes from one foot to the other. The propulsive force is generated by allowing the loaded foot to veer off to the outside of the travel path while the rider falls onto the other foot and, at the final instant of fall, strokes vigorously. The magnitude of the forward force vector component depends on the angular divergence of the track of the loaded foot from the travel path and the vigor of the final stroke.
When ice skating, the resistance to forward motion is determined by the coefficient of friction between the skate blade and the ice. The ice under the blade is usually momentarily melted under the pressure of the blade and the water lubricates the sliding contact, so that the friction is very little. At speed, the air resistance is the dominant drag factor.
When roller skating, the air resistance is the same as for ice skating at the same velocity. However, the rolling friction is generally much greater and depends on the smoothness of the road bed, increasing greatly with surface roughness or particle size.
In the subject device the inner surface of a rolling rim furnishes a smooth rolling surface for a low friction satellite roller which supports the rider. The outer surface or tire of the rim, being much larger in diameter than the satellite roller, rolls much more easily on the roadbed and is less affected by surface roughness than would be the case if the small support roller had to roll directly on the roadbed. Thus, in effect, the rolling rim is continuously and progressively laying down a smooth runway for the smaller support roller. Two other small rollers also ride the inner rim to orient the rider's foot plate within the rim. The foot plate is attached to a light framework that includes the support roller and the two guide follers.
Whereas an earlier device of mono-cycle nature was required to use a large diameter rim to enclose the rider, in the present device it is desired that the diameter of the rolling rims be of smaller size to favor portability of the system. Therefore, while the lower edge of the rim is in contact with the roadway and supports the rider's foot on the footplate and supporting roller, the upper edge of the rim must pass the rider's leg. To accomplish this, the rim is caused to roll at a slight tilt outward so that, while the road contacting point is under the center of the foot, the upper portion of the rim passes outside the leg, being so guided by a shield and light strap which at once secures the rider's foot on the foot plate and the leg with respect to the frame member.
A rim-wheel device is attached, one to each foot of the rider. The propulsive motion is the same as general skating. With this device, where the rims are generally provided with elastic tires, the roller friction is low in the direction of the wheel plane or travel, while the friction of skidding or lateral to the rim, as in the propulsive stroke, is very high. Thus the propulsive efficiency is very high, comparable with ice skating.
Another feature is incorporated which is essential to safety and maneuverability, i.e., effective braking action. Offset from the footplate, both at the heel and the toe, are brake shoes. In normal travel, either propulsive or coasting, the weight is kept level on the footplate and the brake shoes are not in contact with the rim. For braking, the weight is transferred toward the heel of the foot, rotating the footplate about a transverse axis so that the heel is depressed toward the rim, forcing the brake shoe into contact with the rim to the degree required for the desired braking effect. Alternately, either to initiate the initial backward lean or to continue braking, as with the rearward wheel, foot pressure toward the toe can actuate braking. The movement and weight translation is in the natural backward lean for stopping as when walking or running. The degree of lean, which may be accentuated by backward squatting, can provide the balancing force available from the friction of the tire with the roadway. This braking force is available while facing straight on, as with a bicyle, rather than by abrupt turning to provide skidding braking as with roller or ice skating. With a bicycle the stopping deceleration is limited by the height of the center of gravity of the rider above the wheel to road contact. With the new device, squatting posture reduces this limitation. Thus, the braking capability is believed to be much greater than with any of the earlier devices. The competitive advantages of the new propulsive device in relation to prior devices will appear.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which: